The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_physio.c

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    1 /*-
    2  * Copyright (c) 1994 John S. Dyson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  */
   19 
   20 #include <sys/cdefs.h>
   21 __FBSDID("$FreeBSD: releng/10.4/sys/kern/kern_physio.c 290705 2015-11-12 08:47:10Z hselasky $");
   22 
   23 #include <sys/param.h>
   24 #include <sys/systm.h>
   25 #include <sys/bio.h>
   26 #include <sys/buf.h>
   27 #include <sys/conf.h>
   28 #include <sys/malloc.h>
   29 #include <sys/proc.h>
   30 #include <sys/uio.h>
   31 #include <geom/geom.h>
   32 
   33 #include <vm/vm.h>
   34 #include <vm/vm_page.h>
   35 #include <vm/vm_extern.h>
   36 #include <vm/vm_map.h>
   37 
   38 int
   39 physio(struct cdev *dev, struct uio *uio, int ioflag)
   40 {
   41         struct cdevsw *csw;
   42         struct buf *pbuf;
   43         struct bio *bp;
   44         struct vm_page **pages;
   45         caddr_t sa;
   46         u_int iolen, poff;
   47         int error, i, npages, maxpages;
   48         vm_prot_t prot;
   49 
   50         csw = dev->si_devsw;
   51         /* check if character device is being destroyed */
   52         if (csw == NULL)
   53                 return (ENXIO);
   54 
   55         /* XXX: sanity check */
   56         if(dev->si_iosize_max < PAGE_SIZE) {
   57                 printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
   58                     devtoname(dev), dev->si_iosize_max);
   59                 dev->si_iosize_max = DFLTPHYS;
   60         }
   61 
   62         /*
   63          * If the driver does not want I/O to be split, that means that we
   64          * need to reject any requests that will not fit into one buffer.
   65          */
   66         if (dev->si_flags & SI_NOSPLIT &&
   67             (uio->uio_resid > dev->si_iosize_max || uio->uio_resid > MAXPHYS ||
   68             uio->uio_iovcnt > 1)) {
   69                 /*
   70                  * Tell the user why his I/O was rejected.
   71                  */
   72                 if (uio->uio_resid > dev->si_iosize_max)
   73                         uprintf("%s: request size=%zd > si_iosize_max=%d; "
   74                             "cannot split request\n", devtoname(dev),
   75                             uio->uio_resid, dev->si_iosize_max);
   76                 if (uio->uio_resid > MAXPHYS)
   77                         uprintf("%s: request size=%zd > MAXPHYS=%d; "
   78                             "cannot split request\n", devtoname(dev),
   79                             uio->uio_resid, MAXPHYS);
   80                 if (uio->uio_iovcnt > 1)
   81                         uprintf("%s: request vectors=%d > 1; "
   82                             "cannot split request\n", devtoname(dev),
   83                             uio->uio_iovcnt);
   84                 return (EFBIG);
   85         }
   86 
   87         /*
   88          * Keep the process UPAGES from being swapped.  Processes swapped
   89          * out while holding pbufs, used by swapper, may lead to deadlock.
   90          */
   91         PHOLD(curproc);
   92 
   93         bp = g_alloc_bio();
   94         if (uio->uio_segflg != UIO_USERSPACE) {
   95                 pbuf = NULL;
   96                 pages = NULL;
   97         } else if ((dev->si_flags & SI_UNMAPPED) && unmapped_buf_allowed) {
   98                 pbuf = NULL;
   99                 maxpages = btoc(MIN(uio->uio_resid, MAXPHYS)) + 1;
  100                 pages = malloc(sizeof(*pages) * maxpages, M_DEVBUF, M_WAITOK);
  101         } else {
  102                 pbuf = getpbuf(NULL);
  103                 sa = pbuf->b_data;
  104                 maxpages = btoc(MAXPHYS);
  105                 pages = pbuf->b_pages;
  106         }
  107         prot = VM_PROT_READ;
  108         if (uio->uio_rw == UIO_READ)
  109                 prot |= VM_PROT_WRITE;  /* Less backwards than it looks */
  110         error = 0;
  111         for (i = 0; i < uio->uio_iovcnt; i++) {
  112                 while (uio->uio_iov[i].iov_len) {
  113                         bzero(bp, sizeof(*bp));
  114                         if (uio->uio_rw == UIO_READ) {
  115                                 bp->bio_cmd = BIO_READ;
  116                                 curthread->td_ru.ru_inblock++;
  117                         } else {
  118                                 bp->bio_cmd = BIO_WRITE;
  119                                 curthread->td_ru.ru_oublock++;
  120                         }
  121                         bp->bio_offset = uio->uio_offset;
  122                         bp->bio_data = uio->uio_iov[i].iov_base;
  123                         bp->bio_length = uio->uio_iov[i].iov_len;
  124                         if (bp->bio_length > dev->si_iosize_max)
  125                                 bp->bio_length = dev->si_iosize_max;
  126                         if (bp->bio_length > MAXPHYS)
  127                                 bp->bio_length = MAXPHYS;
  128 
  129                         /*
  130                          * Make sure the pbuf can map the request.
  131                          * The pbuf has kvasize = MAXPHYS, so a request
  132                          * larger than MAXPHYS - PAGE_SIZE must be
  133                          * page aligned or it will be fragmented.
  134                          */
  135                         poff = (vm_offset_t)bp->bio_data & PAGE_MASK;
  136                         if (pbuf && bp->bio_length + poff > pbuf->b_kvasize) {
  137                                 if (dev->si_flags & SI_NOSPLIT) {
  138                                         uprintf("%s: request ptr %p is not "
  139                                             "on a page boundary; cannot split "
  140                                             "request\n", devtoname(dev),
  141                                             bp->bio_data);
  142                                         error = EFBIG;
  143                                         goto doerror;
  144                                 }
  145                                 bp->bio_length = pbuf->b_kvasize;
  146                                 if (poff != 0)
  147                                         bp->bio_length -= PAGE_SIZE;
  148                         }
  149 
  150                         bp->bio_bcount = bp->bio_length;
  151                         bp->bio_dev = dev;
  152 
  153                         if (pages) {
  154                                 if ((npages = vm_fault_quick_hold_pages(
  155                                     &curproc->p_vmspace->vm_map,
  156                                     (vm_offset_t)bp->bio_data, bp->bio_length,
  157                                     prot, pages, maxpages)) < 0) {
  158                                         error = EFAULT;
  159                                         goto doerror;
  160                                 }
  161                                 if (pbuf) {
  162                                         pmap_qenter((vm_offset_t)sa,
  163                                             pages, npages);
  164                                         bp->bio_data = sa + poff;
  165                                 } else {
  166                                         bp->bio_ma = pages;
  167                                         bp->bio_ma_n = npages;
  168                                         bp->bio_ma_offset = poff;
  169                                         bp->bio_data = unmapped_buf;
  170                                         bp->bio_flags |= BIO_UNMAPPED;
  171                                 }
  172                         }
  173 
  174                         csw->d_strategy(bp);
  175                         if (uio->uio_rw == UIO_READ)
  176                                 biowait(bp, "physrd");
  177                         else
  178                                 biowait(bp, "physwr");
  179 
  180                         if (pages) {
  181                                 if (pbuf)
  182                                         pmap_qremove((vm_offset_t)sa, npages);
  183                                 vm_page_unhold_pages(pages, npages);
  184                         }
  185 
  186                         iolen = bp->bio_length - bp->bio_resid;
  187                         if (iolen == 0 && !(bp->bio_flags & BIO_ERROR))
  188                                 goto doerror;   /* EOF */
  189                         uio->uio_iov[i].iov_len -= iolen;
  190                         uio->uio_iov[i].iov_base =
  191                             (char *)uio->uio_iov[i].iov_base + iolen;
  192                         uio->uio_resid -= iolen;
  193                         uio->uio_offset += iolen;
  194                         if (bp->bio_flags & BIO_ERROR) {
  195                                 error = bp->bio_error;
  196                                 goto doerror;
  197                         }
  198                 }
  199         }
  200 doerror:
  201         if (pbuf)
  202                 relpbuf(pbuf, NULL);
  203         else if (pages)
  204                 free(pages, M_DEVBUF);
  205         g_destroy_bio(bp);
  206         PRELE(curproc);
  207         return (error);
  208 }

Cache object: b8cdf879c3c4c42a58e2641f43d68c9e


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